Electric system of distribution



April 2, 1940. w s 2,196,043

ELECTRIC SYSTEM OF DISTRIBUTION Fil'd JUQQ 22, 1939 l I v n 8 6 2 I nventor": Robert H. Twiss,

. I I yWd W His ttovney.

Patented Apr. 2, 1940 UNITED. STATES PATENT OFFICE ELECTRIC SYSTEM OF DISTRIBUTION Robert H. Twiss, East Orange, N. 1., assignor to General Electric Company, a corporation of New York Application June 22, 1939, Serial No. 280,531

10 Claims. (01. I'll-97) My invention relates to electric systems of distransformer 4 is permanently connected to the tribution and particularly to alternating current feeder 3, and the secondary winding of the transdistribution systems in which an alternating curformer is adapted to be connected to the network rent network is supplied with current by means by suitable switching means 5. The feeder 3 is 5 of a plurality of feeders containing distribution adapted to be connected to the supply circuit 2 5 transformers. In alternating current distribuby suitable switching means 6. As shown in tion systems of this type network protectors are the drawing, the switching means 5 and 6 are provided for controlling the connections between latched-in circuit breakers and are respectively the secondary winding of each transformer and provided with closing coils l and 8 andtrip coils m the network. Each network protector includes 9 and I0. 10 a. network circuit breaker controlled by a power v A power directional relay ii is provided for directional relay which is arranged to effect the controlling the opening of the circuit breaker 5. opening of the network circuit breaker when the This power directional relay is connected in any power flow from the network to the feeder exsuitable manner to the secondary winding of the u ceeds a predetermined amount. In order to pretransformer 4 so that the relay is energized in vent the circuit breaker from being opened under accordance with the power flow between the netcertain operating conditions which sometimes work and the transformer. As shown in the occur under light load conditions, it is the pracdrawing, the relay comprises voltage windings l4 tice in some installations to desensitize the diwhich are connected to be energized from the m rectional relay by means of a restraining windnetwork side of the circuit breaker 5 and cooping which is energized by the network voltage so crating current windings l5 which are connected that the amount of reverse power required to opto be energized from current transformers l6 erate the directional relay varies with the neton the feeder side of the circuit breaker 5. The work voltage. However, with such an arrangerelay is also provided with suitable restraining ment it is not possible to eflect the opening of or desensitizing means which is illustrated as two 25 the network circuit breaker by merely disconvoltage windings l1 energized from the secondnecting the associated feeder from its supply cirary winding of the transformer 4 by means of a cuit because the reverse magnetizing current of potential transformer I8. These restraining the associated distribution transformer is less windings exert a torque which opposes the torque than the amount of reverse current required to exerted by the voltage and current windings 3 effect the operation of-the directional relay. when power flows from the network to the feed- One object of my invention is to provide in er. Normally the relay II is biased so that its an alternating current distribution system of the closing contacts 19 are closed and its tripping above mentioned type an arrangement for contacts 20 are open. When the current flow changing the reverse power setting of the difrom the network I to the transformer 4 is above 35 rectional relay when the associated feeder is a predetermined amount the relay closes its condisconnected from its supply circuit so that the tacts 20 and opens its contacts I9. In the parrelay can respond to the reverse magnetizing ticular arrangement disclosed in the drawing the current in the feeder to effect the opening of the amount of reverse current required to cause the 40 associated network circuit breaker. relay II to open its contacts i9 and close its 40 My invention will be better understood from contacts 20 is greater than the magnetizing ourthe following description when taken in connecrent of the transformer 4 so that merely opention with the accompanying drawing which diing the circuit breaker 6 in the feeder 3 does not agrammatically illustrates a system of electric cause sumcient reverse current to flow to cause 5 distribution embodying my invention, and its the relay II to close its contacts 20. A fault on scope will be pointed out in the appended claims. the feeder 3, however, causes suflicient reverse Referring to the drawing, i represents a low current flow to operate the relay II so that it voltage alternating current network which is closes its contacts 20. adapted to be supplied with current from a suit- In accordance with my invention, I provide go able source of current shown as a supply circuit means whereby the sensitivity of response of the o 2 by means of a plurality of feeders I only one relay II can be increased when the circuit breakof which is shown in the drawing in order to er 6 is open so that the relay can respond to the simplify the disclosure. A transformer 4 is proreverse magnetizing current of the associated vided for supplying current from the feeder 3 to transformer 4 to efiect the opening of the assou the network 'i. The primary winding of the elated circuit breaker I. In the particular embodiment shown in the drawing, this means comprises a pilot circuit which is arranged to be completed through auxiliary contacts 25 on the circuit breaker 6 when it is open and a relay 24 in said pilot circuit, which, when energized, interrupts the circuit of the restraining windings l1 so as to decrease the reverse current setting of the relay ll. Any suitable source of current such as a battery 26 may be included in the pilot circuit for energizing the relay 24 and preferably a suitable control switch 21 is also included in the pilot circuit whereby the pilot circuit may be interrupted even when the switch 6 is open.

The operation of the arrangement shown is as follows:

Normally the reverse current setting of the relay H with the restraining windings ll energized is so high that sufficient current to cause the relay H to close its contacts and complete an energizing circuit for the trip coil 9 of the circuit breaker 5 only flows when a fault occurs on the feeder 3. When, however, it is desired to isolate the feeder 3 from the network i under normal conditions of the feeder, an energizing circuit for the trip coil iii of the circuit breaker 5 is completed in any suitable manner so as to open the circuit breaker 6 and disconnect the feeder 3 from the supply circuit i. When the circuit breaker 6 opens, its auxiliary contacts complete an energizing circuit for the control relay 24 so that it interrupts the circuit of the restraining windings i1 and thereby increases the sensitivity of the relay II in order that the reverse magnetizing current supplied from the network I to the transformer 4 may cause the relay to close its contacts 20. The closing of the contacts 20 of the relay ll completes an energizing circuit for the trip coil 5 of the associated circuit breaker 5 through its auxiliary contacts 28 so that it opens and disconnects the feeder 3 from the network I.

While I have, in accordance with the patent statutes, shown and described my invention as applied to a particular system and as embodying various devices diagrammatically indicated, changes and modifications will be obvious to those skilled in the art, and I therefore aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, an alternating current network, a feeder circuit, a switch connecting said network to said feeder circuit, power directional means normally responsive to a predetermined amount of power flow from said network to said feeder circuit for controlling the opening of said switch, a second switch in said feeder circuit, means for opening said second switch, a pilot circuit, means for effecting a predetermined change in the energization of said pilot circuit when said second switch is open, and means responsive to said predetermined change in the energization of said pilot circuit for changing the sensitiveness of said power directional means.

2. In combination, an alternating current network, a feeder circuit, a switch connecting said network to said feeder circuit, power directional means normally responsive to a predetermined amount of power flow from said network to said feeder circuit for controlling the opening of said switch, a second switch in said feeder circuit, means for opening said second switch, a normally deenergized pilot circuit, means for energizing said pilot circuit when said second switch is open, and means responsive to the energization of said pilot circuit for changing the sensitiveness of said power directional means.

3. In combination, an alternating current network, a feeder circuit, a switch connecting said network to said feeder circuit, control means for said switch including normally insensitive directional means responsive to the flow of power flow through said switch, a second switch in said feeder circuit, means for opening said second switch, a pilot circuit, means for effecting a change in the energization of said pilot circuit when said second switch is open, and means responsive to said change in the energization of said pilot circuit for increasing the sensitiveness of said directional means to currents of a predetermined direction.

4. In combination, an alternating current network, a feeder circuit, a switch connecting said network to said feeder circuit, control means for said switch including normally insensitive directional means responsive to the flow'of power flow through said switch, a second switch in said feeder circuit, means for opening said second switch, a normally deenergized pilot circuit, means responsive to the opening of said second switch for effecting the energization of said pilot circuit, and means responsive to the energization of said pilot circuit for increasing the sensitiveness of said directional means to currents of a predetermined direction.

5. In combination, an alternating current network, a feeder circuit, a switch connecting said network to said feeder circuit, control means for said switch including a power directional relay normally responsive to power flow of more than a predetermined amount from said network to said feeder circuit, a second switch in said feeder circuit, means for opening said second switch, a pilot circuit, means for changing the energization of said pilot circuit in a predetermined manner when said second switch is open, and means responsive to said change in the energization of said pilot circuit for modifying the sensitiveness of said relay so that it responds to a smaller amount of powerflow from said network to said feeder circuit.

6. In combination, an alternating current network, a feeder circuit, a switch connecting said network to said feeder circuit, control means for said switch including a power directional relay normally responsive to power flow of more than a predetermined amount from said network to said feeder circuit, a second switch in said feeder circuit, means for opening said second switch, a pilot circuit, means for energizing said pilot circuit when said second switch is open, and means responsive to the energization of said pilot circuit for modifying the sensitiveness of said relay so that it responds to a smaller amount of power flow from said network to said feeder circuit. I

7. In combination, an alternating current network, a feeder circuit, a switch connecting said network to said feeder circuit, a supply circuit connected to said feeder circuit, control means for said switch including a power directional relay normally responsive to power flow of more than a predetermined amount from said network to said feeder circuit, means for disconnecting said feeder circuit from said supply circuit and for effecting a change in the energization of said pilot circuit, and means responsive to said change in the energization of said pilot circuit for modifying the sensitiveness of said relay so that it responds to a smaller amount of power flow from said network tosaid feeder'circuitr 8. In combination, an alternating current network, a feeder circuit, a switch connecting said network to said feeder circuit, a supply circuit connected to said feeder circuit. control means for said switch including a power directional relay normally responsive to power flow of more than a predetermined amount from said network to said feeder circuit, means for disconnecting said feeder circuit from said supply circuit and for increasing the energization of said pilot circuit, and means responsive to said increase in the energization of said pilot circuit for modifying the sensitiveness of said relay to the flow of power from said network to said feeder circuit.

9. In combination, an alternating current network, a feeder circuit including a transformer 30 having primary and secondary windings, a switch connecting the secondary winding of said transformer to said network, a supply circuit, a second switch connecting the primary winding of said transformer to said supply circuit, power direc- 25 t'lonal means normally responsive to an amount.

of power flow from said network to the secondary winding of said transformer in excess of the amount of reverse power flow due to magnetizing said transformer from the network, means con- 30 trolled by said power directional means for opening said first mentioned switch, means for opening said second switch, a pilot circuit, means responsive to the opening of said first mentioned switch for 'eflecting a predetermined change in the energization of said pilot circuit, and means responsive to said predetermined change in the energization of said pilot circuit for changi g the sensitiveness of said power. directionalmeans so 5 that it responds to the amount of reverse power supplied to said transformer when said transformer is magnetized from said network.

10. In combination, an alternating current network, a feeder circuit including a transformer 10 having primary and secondary windings, a switch connecting the secondary winding of said transformer to said network, a supply circuit, a second switch connecting the primary winding of said transformer to said supply circuit, power direc- 15 I tional means normally responsive to an amount of power flow from said network to thesecondary winding of said transformer in excess of the amount of reverse power flow due to magnetizing said transformer from the network, means controlled by said power directional means for open ing said first mentioned switch, means for openin! said second switch, a normally deenergized pilot circuit, means responsive to the opening of said first mentioned switch for energizing said pilot circuit, and means responsive to the energization of said pilot circuit for changing the sensitiveness of said power directional means so that it responds to the amount of reverse power supplied to said transformer when said' transformer is magnetized from said network.

ROBERT E. TWISS. 

